The present invention relates to combine harvesters and more particularly to improvements in the cleaning apparatus of combine harvesters which improve substantially the crop cleaning characteristics thereof, epecially when the machines are operating on terrain that is inclined from the horizontal. Although the invention is useful on all known types of combines, it is particularly beneficial when provided on axial flow type combines which do not utilize the well known conventional straw walkers.
Conventional combine harvesters have as part of the grain cleaning mechanism a so-called grain pan which is disposed below the threshing and separating mechanism for collecting grain kernels, chaff and tailings (unthreshed heads) separated from the straw in said threshing and separating mechanism. The grain pan is arranged to supply material collected thereon to cleaning sieves which are reciprocated in a fore-and-aft direction in the path of a rearwardly and upwardly directed cleaning air blast from a cleaning fan disposed below the grain pan and below and forwardly of the cleaning sieves to separate the kernels from the chaff and the tailings. The small, relatively heavy kernels pass through the sieves and are collected therebeneath. The light chaff is blown out of the rear end of the cleaning mechanism and the tailings, being too large to pass through the sieves are too heavy to be blown with the chaff, drop from the rear edges of the sieves and are collected for rethreshing.
Axial flow type of combine harvesters use a grain pan of some type underlying the threshing and separating mechanism, typically one or two rotors, in conjunction with cleaning sieves which usually are reciprocatable. A cleaning fan blows upwardly from below the grain pan thru the sieves. Variations in axial flow cleaning systems have employed transfer or distribution augers and accelerator rolls in attempts to solve the problems created by operating combine harvesters on inclined terrain.
It is obvious that the efficiency of a cleaning system in a combine is greater if the crop material is continuously fed to the sieves and the cleaning air blast from the cleaning fan is uninterrupted. As a rule this is achieved only if the combine harvester is in a virtually horizontal position. Where the ground is irregular, particularly on slopes, different things can happen in the cleaning mechanism, dependent upon a number of factors, such as the degree to which the combine is inclined from the horizontal. If the combine is operating downhill crop material may pile up on the grain pan and/or on the lower points of sieves. This situation can prevent the crop material from being cleaned properly and clogging may occur within the cleaning mechanism. On the other hand, if the combine is operating uphill, crop material can pass too rapidly over the sieves and grain will be spilled over the rear edges of the sieves, instead of passing through them. This will result in unacceptable grain losses.
When the combine harvester is working inclined relative to the horizontal and inclined transversely in relation to the direction of travel, crop material separated from the straw in the threshing and separating means tends to move to the lower side of the grain pan. This sideward shifting of crop material is continued during its transport along the grain pan, during its transfer from the grain pan to the cleaning sieves, during its movement across the cleaning sieves and during its dropping from one sieve to another sieve disposed therebelow. The result of all this is that the higher or uphill sides of the sieves are virtually free of crop material while the lower sides of the sieves are so heavily loaded with crop material that clogging may occur. This, in turn, results in grain emerging from the combine harvester at the rear instead of passing through the sieves to the clean grain trough for transport to the grain tank. This situation results in considerable grain losses at the lower or downhill side of the sieves. Also, with uneven loading of the sieves the cleaning air blast is unequally effective, so that the effect of cleaning is further considerably diminished. Indeed, cleaning air tends to escape through the underloaded sieve sections, thus leaving the overloaded sieve sections with reduced air blasts.
A great many devices have been utilized in the past to take care of these conditions. However, none of them have been fully satisfying in all respects.
When operating up and down the incline, the loading of the sieves remains substantially equal in the transverse direction. As previously described, either the accumulation of crop material at a forward end of the sieves or the too fast movement of crop material over the sieves towards the rear will result in excessive grain losses and substantially reduced efficiency of the harvester. These problems can be fairly easily overcome either by increasing the air blast, particularly at the forward ends of the sieves, when operating downhill or by reducing the air blast when operating uphill. These corrective measures are accomplished by either appropriately increasing or decreasing the cleaning fan speed. In order to permit such adjustments to be accomplished while the combine is operating, the fan speed is made adjustable from the operator's platform.
The problems are substantially more difficult when the combine harvester is operated on inclines which are transverse to the direction of travel under conditions when uneven sieve loading in a transverse direction is experienced.
One approach which has been taken to solve the aforementioned problems, tilts the entire combine body in one or other direction with respect to the wheels and the header to keep the cleaning means level. This approach has been found to be very effective in many cases. However, it is a very complicated and expensive approach.
Other prior art approaches have kept sections of the cleaning sieves, or the entire cleaning sieves, as well as the entire cleaning shoe, level. These approaches in conventional combine harvesters using straw walkers generally employ means for counterbalancing the sieves, cleaning shoe or sieve sections about fore-and-aft extending axes to provide instantaneous reaction to the tilting of the combine harvester transversely to the direction of travel. While the concept of counterbalancing about fore-and-aft axes is sound, the known devices to carry out this concept are not wholly satisfactory for one reason or another. As mentioned before, it is not only necessary to maintain the sieves level in transverse direction, but it is equally important that the air blast therethrough be maintained uniformly in the transverse direction at all times. The leveling devices suggested in the past have either ignored this problem completely, or have attempted to solve it by providing adjustable air deflecting means in the air stream which react to the leveling action of the counterbalancing to alter the direction of the air stream. Such an alteration of the air stream does have a beneficial result, but still does not wholly solve the problem, since deflecting the air with wind boards situated in the air stream, the volume and velocity of the air is altered, as well as the direction. This change in volume and velocity is not desirable.
Also, the layer of crop material supplied to the cleaning sieves should be kept substantially of even thickness transversely across the cleaning sieves. In certain proposed solutions adjustable crop deflecting means are arranged on the grain pan which react to the transverse inclination of the machine to direct crop material towards the higher side of the cleaning sieves.
In still another approach, it has been proposed to let both the cleaning sieves and the cleaning fan level in unison so that at all times the same relationship exists between the cleaning fan and the cleaning sieves. In one such arrangement the cleaning shoe together with the cleaning fan housing are pivotally mounted around the fan axis. The leveling device provided in this arrangement causes the cleaning shoe to remain substantially level in fore-and-aft direction only and thus the more critical transverse leveling is not accomplished. Also, as stated previously, the necessity for leveling the cleaning device lengthwise of the machine can be avoided in a fairly inexpensive way by making the fan speed adjustable from the operator's platform.
In still another approach, the cleaning shoe and the cleaning fan are mounted for transverse leveling in unison as the machine is tilted transversely to the horizontal during operation. In this known arrangement the relationship between the cleaning fan and the cleaning sieves remains unvaried. However, certain problems still occur in as far as the problems associated with the grain pan on the one hand and the transfer from the grain pan to the sieves on the other hand are not yet solved. Also, the transfer of the clean grain and the tailings from the cleaning mechanism to the remainder of the machine causes problems because the transfer area movement of grain and tailings may not be continuous or crop losses may occur.
The aforementioned problems are solved in the design of the cleaning system of the present invention for both conventional combines using a transverse threshing cylinder and straw walkers or the more recent axial flow type of combines by providing in a combine harvester a cleaning device with a cleaning efficiency which remains continuously high even when operating on uneven ground.